In the cold waving of hair it is common practice to soften or treat the hair with a reducing solution which permits shaping of the hair on a mandrel such as a curling rod, and then applying an oxidizing agent to the treated hair to neutralize the unreacted reducing agent and restore the strength of the hair. Unfortunately the oxidizing agent usually does not completely oxidize the reducing agent and completely restore the strength of the hair. Therefore, hair treated by conventional cold waving processes is left somewhat limp.
U.S. Pat. No. 3,266,994 describes a two step method where a water-soluble, non-toxic salt of a polyvalent metal is added to an aqueous solution of the oxidizing agent to increase the strength of treated hair.
U.S. Pat. No. 3,227,615 describes another method aimed at overcoming the problem of limp hair resulting from waving processes. This patent discloses a one step waving process whereby only a polyamide resin and a bisulfite salt are used to treat the hair.
Although these two processes marginally improve the quality of the treated hair, they do not give limp hair the strength, resiliency and body of healthy normal hair.